New preliminary and published data obtained during the last funding period has led to the novel hypothesis that the immune activity of Antigen Presenting Cells (APCs; macrophages and dendritic cells), can be stimulated by physiologically relevant thermal gradients. Because of the critical, central role these cells play in linking the innate and adaptive immune responses and in generation of long term memory responses, understanding fully the potential for APC regulation by mild (fever-range) hyperthermia could provide the essential platform of information needed for next generation protocols utilizing strategic applications of hyperthermia for the treatment of cancer. Data presented indicate that mild whole body hyperthermia speeds delayed type hypersensitivity reactions and enhances tumor control. Importantly, it also increases the production of immunostimulatory cytokines and nitric oxide and increases expression of critical cell surface molecules e.g. MHC molecules needed for activation of T lymphocytes. However, we know little about either the precise magnitude of thermal enhancement of the immune response or effects of varying the timing of its application. Further, we know very little about transcriptional/translational control of relevant genes and proteins affected by thermal stimuli. Obtaining this information is critical for rational development of new clinical protocols. The aims of this grant will: Aim 1) identify precisely the magnitude of the contribution of thermal stimuli administered at different times on APC function in the immune response using a well-defined antigen (ovalbumin) for which there are tools already available for dissecting the immune response, Aim 2) test the hypothesis that genes/proteins known to be involved in the immune responses defined in Aim 1 are up regulated and 3) determine transcriptional and translational processes by which thermal stimuli are able to increase production of immunostimulatory molecules (e.g., nitric oxide). Importantly, in each aim, we will use physiologically relevant APCs that infiltrate normal tissues, tumors and draining lymph nodes in mice that undergo whole body hyperthermia rather than just studying long-term cell lines, which may have lost normal thermal regulatory responses after long periods of growth in vitro. As the goals of this proposal are met and we come to understand better the biological effects of mild temperature increases on APC function, we will be able to rationally design improved clinical strategies in order to maximize the anti-tumor potential of a patient's immune response.